Dart Programming Interview Questions and Answers

Dart is an open source, structured Web programming language developed by Google. It is used to build web, server and mobile applications. Google intended this Web programming language to replace JavaScript, as it addresses several key problems with the JavaScript language.

• Dart is a class-based programming language.
• It is an object-oriented, single inheritance.
• Dart supports interfaces and abstract classes, reified generics
• Dart used Single threaded (asynchronous)
• Optional typing / type annotations

• Dart run in First Command-line using Dart VM
• In a browser in Dart VM (Chromium + Dart = Dartium)
• Compiled to JavaScript in any browser. (dart2js)

Dart syntax is:

Main () {

Print (`Hello World’);

}

Output: Hello world

Libraries: In Dart, libraries is used to support web and web server development. Dart libraries not only provide APIs, but it is a unit of privacy: they can implement details such as private variables. There are some of libraries of Dart:

• I/O Library: Read and write files.
• Dart core: data structure and operations.
• Dart async: Support for asynchronous programming, with classes such as Future and Stream.
• Dart math: Mathematical constants and functions, plus a random number generator.
• Html Library: HTML5 DOM.
• Isolate Library: spawning and communicating with isolates
• Crypto Library: SHA1, MD5, SHA256 and HMAC support.
• Json Library: parse and produce JSON-encoded text.
• Unit Test Library: function and classes.
• Dart convert: Encoders and decoders for converting between different data representations, including JSON and UTF-8.

The Dart programming language supports the following types:

Numbers: In Dart, int, double are used.

Strings: A Dart string is a sequence of UTF-16 code units. You can use either single or double quotes to create a string

Booleans: Dart uses the bool keyword to represent a Boolean value

Lists: A List is an ordered group of objects.

Maps: The Map data type represents a set of values as key value pairs.

Dynamic Type: The dynamic keyword can also be used as a type annotation explicitly.

The “this” reserved word denotes the target of access current member invocation. You can use this in a factory constructor, static member or method. The “this” keyword references the current instance.

Syntax: this.name

In Dart, A typedef (Or function types alias) helps to define pointer to execute code within memory.

Syntax: typedef function_name (parameters)

Strings: Strings represent a sequence of characters. For instance, if you were to store some data like name, address etc. the string data type should be used. A Dart string is a sequence of UTF-16 code units. You can use either single or double quotes to create a string:

var s1 = ‘Single quotes work well for string literals.’;

var s2 = “Double quotes work just as well.”;

var s3 = ‘It\’s easy to escape the string delimiter.’;

var s4 = “It’s even easier to use the other delimiter.”;

Pub also includes commands for creating, developing, and deploying Dart applications. Pub is a tool for manage Dart packages.

Dart getters and setter’s method provide read and write functionality. Getter and setter method using the get and set keyword. The get keyword is used for reading a value and set keyword is used for writing a value. Getters and Setters is also known as accessors and mutators. It allows the program to initialize and retrieve the values of class fields.

Snapshots: Snapshots are a core part of the Dart VM. Snapshots are files which store objects and other runtime data. There are three type of snapshots:

Script snapshots: Dart programs can be compiled into snapshot files. These files contain all of the program code and dependencies preparsed and ready to execute. This allows fast startups.

Full snapshots: The Dart core libraries can be compiled into a snapshot file which allows fast loading of the libraries. Most standard distributions of the main Dart VM have a prebuilt snapshot for the core libraries which is loaded at runtime.

Object snapshots: art is a very asynchronous language. With this, it uses isolates for concurrency. Since these are workers which pass messages, it needs a way to serialize a message. This is done using a snapshot, which is generated from a given object, and then this is transferred to another isolate for deserializing.

In Dart, Method Overriding is a technique that child class redefines a method in its parent class. In overriding, a method in a parent class is overridden in the child class. The method in the child class will have the same signature as that of the parent class. Since the method in the child class has the same signature & name as the method of its parent class, it is termed as overriding.

Example:

Void main () {  

   Child c = new Child ();  

   c.m1 (12);  

}  

Class Parent {  

   Void m1 (int a) {print (“value of a “) ;}  

}   

Class Child extends Parent {  

   @override  

   Void m1 (int b) {  

      Print (“value of b “);  

An interface defines how one may interact with an object. In interface you can declare a abstract method (means you can declare body in its sub class), basically it is used for solving the problem of multiple inheritance.

Syntax of interface:

Interfaceidentifierinterfacename{//………AbstractMethod……………..//} e.g, interface MyInterface {AbstactMethod () ;}

The statements which allow us to control the flow of our program, rather than execution every one of code in the order it appears in the program. Some of control flow statements is given below.

Assert statements: A assert statements is work in dart like a if statements, it disrupt normal execution if a Boolean condition is false.

Break statement: The break statement is used in dart when we want to exit out from any for, while, do-while loops, or any statements like switch.

Continue statement: The continue statement is similar to break, it is also used in for, while, do-while, it exit from the current iteration of the loop and execution will start from beginning of the loop.

The following is the syntax to declare class:

Class class name {   

   <fields>  

   <getters/setters>  

   <constructors>  

   <functions>  

In Dart, Truncate method is used to return an integer after discarding any fractions digits.

Example:

Void main () {  

   Double n1 = 2.123;  

   Var value = n1.truncate ();  

   Print (“The truncated value of 2.123 = “);  

}  

There are two types of list in Dart that are given below:

Fixed Length List: (length fixed)

Growable List: (Length can change at runtime.

There are the following steps, which is helpful for creating a web application in DART for new users:

• First download a DART software, who is supported by your operating system.
• After download and installing your Dart software, choose a New Application in file menu from your DART software.
• And after it, you write a web application name in front of given name index.
• Set a directory, where you want to save your web application.
• Next, you have two radio button in a DART, one for command line application and second one for web application, if you want to create a web application then must be choose a web application.
• After the compilation of all these step you click on the finish button. Then you find out a automatically created a web application. If you want then you can edit it, according to your desire output.

There are different types of error will be generates. Here

• Static warnings
• Dynamic errors
• Compile Time errors
• Runtime error

A Lambda function is a concise mechanism to represent functions. These functions are known as Arrow functions.

Example:

Void main () {  

 PrintMsg ();  

   Print (test ());  

}   

PrintMsg () => 

Print (“hello”);  

int test ()=>123;                        

// returning function 

Dart iso-server display web server library that dynamically loads code from filesystem to handle HTTp requests. The purpose of iso server:

• To show, how to dynamically load scripts into an isolate.
• Pay with one may to build a ‘hot-swapping’ server.

Inheritance can be of the following three types:

Single: Every class can at the most extend from one parent class

Multiple: A class can inherit from multiple classes. Dart doesn’t support multiple inheritance.

Multi-level: A class can inherit from another child class.

The following command is used to compile Dart into JavaScript:

dart2js - - out=<output_file>.js  <dart_script>.dart

Classes and interface: DART also provide the better functionality of classes and interface, you can use it like an object-based programming language.

Inheritance: classes is present and therefore does now the extends keyword. Pretty damn simple in compression to JavaScript.

Dart can work with types: In Dart if you want to work with types, just enable the type checker and go ahead.

Global namespace: Dart have libraries, means if you have a keyword library, you must be understood by what is public visible outside of it.

Dart knows concurrency: Dart knows isolate, but JavaScript thing are not concurrent.

Dart knows foreach: In JavaScript for each loop is not present, but you can use foreach in dart.